In recent years, organic light-emitting diode (OLED) display panels have become novel flat display panels which are popular at home and abroad. Compared to LCD panels as the mainstream of flat display panels, OLED display panels have intrinsic advantages, such as self-luminescence, wide view angle, short response time, wide gamut, low working voltage, thin panel, easiness of being made into a flexible panel, wide range of working temperature.
However, there will be a microcavity effect more or less, whether in a top emission type OLED display panel or in a bottom emission type OLED display panel. The microcavity effect mainly means that photon densities of different energy states are redistributed such that only the light having a specific wavelength is emitted at a specific angle after complying with the resonant cavity mode. As for a top emission type OLED display panel, the anode close to the base substrate has a very high reflectance, and the cathode away from the base substrate typically uses a semitransparent metal structure, which may also increase the reflection of light. Therefore, the interference of multiple photon beams will be formed between the anode and the cathode, such that the microcavity effect is more remarkable. In a top emission type OLED display panel in the prior art as shown in FIG. 1, a light-emitting unit 20 comprises a first electrode 21, a light-emitting layer 22, and a second electrode 23, which are sequentially provided above a base substrate 10. A microcavity is composed of the first electrode 21, the light-emitting layer 22, and the second electrode 23. The emergence direction of the light beam is perpendicular to the interface between the first electrode 21 and the light-emitting layer 22 and the interface between the light-emitting layer 22 and the second electrode 23. This results in problems, such as narrow view angle, different light intensities seen at different observation angles, and relatively small light-emitting area.